1. Field of the Invention
The invention relates to a process for producing semiconductor devices and somewhat more particularly to a process of producing semiconductor devices wherein a trench or groove-like recess is produced in the surface of a Si layer and the Si surface along at least one edge of such a recess is masked with a heat-resistant oxidation-blocking or oxidation impermeable layer so that when the resultant structure is subjected to thermal oxidation, only the unmasked Si surface areas, generally within the recesses, are coated with a relatively thick SiO.sub.2 layer.
2. Prior Art
Philips Research Reports, Vol. 25, April 1970, pages 118-132 and Vol. 26, June 1971, pages 157-165 as well as Electronics, Jan. 3, 1971, pages 52-55, suggest methods of producing semiconductor devices via a so-called local oxidation technique with the aid of silicon-nitride films and/or SiO.sub.2 --Si.sub.3 N.sub.4 sandwich film structures whereby relatively well defined and thick oxide patterns are produced, which may be partially or fully countersunk in a Si surface. However, these prior art techniques cause an indeterminate edge condition to occur at the juncture of the Si surface and the SiO.sub.2 pattern. Such indeterminate edge conditions are detrimental to the electrical characteristics of semiconductor devices containing such indeterminate edges.